1. Field of the Invention
The present invention relates to a heat insulation covering structure for a cargo tank for containing an extremely low temperature liquefied natural gas (LNG) or the like which requires heat insulation while in storage. The tank structure includes a cylindrical vessel, a rectangular vessel or the like. In particular, the present invention is related to a heat insulation covering structure for a low temperature cargo tank, the structure of which is preferable for the insulation covering of a spherical vessel (spherical tank) used in a LNG cargo ship or the like.
2. Description of the Related Art
Heretofore, with a spherical tank for storing an extremely low temperature LNG at about -160.degree. C., as shown in FIG. 12, many different kinds of heat insulating panels (covering member) 2 are fixed to a tank 1 with a bolt or the like. The panel being developed on a surface of the spherical tank 1, formed of aluminum or the like, for each member of the tank surface and is then processed into a complicated curved surface so as to conform to each member. After that resin such as polyurethane or the like is applied between joining parts of each heat insulating panel 2 to provide heat insulation and covering.
Consequently, a heat insulation covering for a conventional spherical tank, a heat insulating panel 2 is used which is preliminarily fabricated into a configuration which conforms to the shape of each member of the tank surface. In addition, each of the heat insulating panels 2 is formed by assembling in various ways heat insulating materials, reinforcements, and soft heat insulating materials so as to be able to endure extremely low temperatures. Further, there arises a problem in that a large number of manhours are needed for applying the resin-made bonding materials 14 into connection joints to connect each heat insulating panel 2 to another at the time of mounting the heat insulating panels 2.